The present invention relates to pneumatic nebulizers and, in particular, it concerns a pneumatic nebulizer in which aerosol mist is produced in a downwardly flowing direction, the aerosol mist then leaves the nebulizer through a downwardly projecting aerosol outlet.
It is known to provide a nebulizer for the production of a high volume of aerosol for inhalent delivery of medications. In general pneumatic nebulizers atomize liquids by introducing small amounts of the liquid into a flow of high velocity air, which serves to break up the liquid into small droplets. Usually, the liquid is as drawn from a reservoir and aspirated into the airflow by means of a venturi effect created by structural elements of the device. The air and liquid mixture then continues in an upward direction to an aerosol outlet. The medicated aerosol mist is then administered to a patient by means of a therapeutic inhalation interface or by discharge of the mist into the ambient air for direct inhalation by the patient. This upward flow has become the generally accepted means for keeping drops that are too large from continuing with the upward airflow. The larger drops are then drawn by gravity back into the reservoir. This style of nebulizer in herein referred to as an “up draft” nebulizer.
Some pneumatic nebulizers, such as the up draft nebulizer of U.S. Pat. No. 6,338,443, add an additional step of impacting the high velocity air and liquid mixture onto a solid surface so as to further break up the liquid into smaller droplets, which are then drawn out through the aerosol outlet. Here too, drop which are too large fall back into the reservoir region from the force of gravity.
The nebulizer disclosed in U.S. Pat. No. 5,490,630 has a side directed aerosol outlet, herein referred to as a “side draft” nebulizer, and includes an atomization stage in which a liquid is aspirated into a downward flowing jet of air. The air/liquid mixture in then impinged upon a solid structural surface to further atomize the droplets as the flow path continues in a downward direction. The flow path is then directed upwardly toward the side directed aerosol outlet. The change of direction is used in this device as a means of separating out the larger drops from the aerosol mist.
It is obvious by their designs that the above mentioned devices are intended for deployment at a designated orientation, and that proper function is limited to a relatively small range of variance from the designated orientation. In practical use, however, it would sometimes advantageous to deploy a nebulizer at an orientation outside the tolerances of these devices. U.S. Pat. No. 4,512,341 to Lester suggests a solution by disclosing a nebulizer that is operational at any orientation between vertical and horizontal. The vertical orientation, however, is referring to an up draft configuration, therefore '341 discloses a nebulizer that is usable as both an up draft and side draft nebulizer, and any orientation in between.
Further, WO0202052, to the present inventor, discloses an aerosol inhalation interface that is suspended above the patient. It should be obvious to one ordinarily skilled in the art that while the inhalation interface of WO0202052 will function with excellent results using either up draft or side draft nebulizers, it would be preferable to use such an interface in concert with a “downdraft” nebulizer. There are also numerous applications in which downwardly directed flow of medicated aerosol is preferable.
There are also known devices generally referred to as inhalers that are used by some patients, such as asthmatics, suffering respiratory distress. These devices typically consist of a pressurized vial from which a jet of medicated droplets is discharged in a downward direction into a side opening mouthpiece. These devices, however, are intended for delivery of medicated spray over a short time span, generally less than one second in duration. That is to say, a short burst of spray. Devices of this type are not structurally nor mechanically suited, nor are they intended for delivery for an extended time period of several minutes, nor do they teach nor suggest such application.
There is therefore a need for a nebulizer having a downwardly facing aerosol outlet that is structurally configured so as to produce aerosol mist in a downward direction and that delivers a downwardly directed flow of medicated aerosol mist for a period of time. That is to say, a downdraft nebulizer.